The largest of all seals, elephant seals rank among the most impressive of marine mammals. They are renowned for their spectacular recovery from near-extinction at the end of the nineteenth century when seal hunters nearly eliminated the entire northern species. No other vertebrate has come so close to extinction and made such a complete recovery. The physiological extremes that elephant seals can tolerate are also remarkable: females fast for a month while lactating, and the largest breeding males fast for over one hundred days during the breeding seasons, at which times both sexes lose forty percent of their body weight. Elephant seals dive constantly during their long foraging migrations, spending more time under water than most whales and diving deeper and longer than any other marine mammal. This first book-length discussion of elephant seals brings together worldwide expertise from scientists who describe and debate recent research, including the history and status of various populations, their life-history tactics, and other findings obtained with the help of modern microcomputer diving instruments attached to free-ranging seals. Essential for all marine mammalogists for its information and its methodological innovations, Elephant Seals will also illuminate current debates about species extinctions and possible means of preventing them. The largest of all seals, elephant seals rank among the most impressive of marine mammals. They are renowned for their spectacular recovery from near-extinction at the end of the nineteenth century when seal hunters nearly eliminated the entire northern species. No other vertebrate has come so close to extinction and made such a complete recovery. The physiological extremes that elephant seals can tolerate are also remarkable: females fast for a month while lactating, and the largest breeding males fast for over one hundred days during the breeding seasons, at which times both sexes lose forty percent of their body weight. Elephant seals dive constantly during their long foraging migrations, spending more time under water than most whales and diving deeper and longer than any other marine mammal. This first book-length discussion of elephant seals brings together worldwide expertise from scientists who describe and debate recent research, including the history and status of various populations, their life-history tactics, and other findings obtained with the help of modern microcomputer diving instruments attached to free-ranging seals. Essential for all marine mammalogists for its information and its methodological innovations, Elephant Seals will also illuminate current debates about species extinctions and possible means of preventing them.